Conventionally, an operability range display device for displaying the range that a work machine is capable of reaching is known. For example, Japanese Laid-open Patent Application Publication 2001-98585 discloses a digging work guidance device. The guidance device displays a side view of a hydraulic shovel and a cross section of a design land shape constituting a work object on a screen. An operability range showing the range of motion of a bucket is also displayed on the screen.
Meanwhile, Japanese Laid-open Utility Model Application Publication H2-30521 discloses a safety device for a digging construction machine. This safety device, like the guidance device disclosed in Japanese Laid-open Patent Application Publication 2001-98585, calculates the operability range of a bucket. The area beneath a track is calculated as a warning area in which intrusion of the tip of the bucket is prohibited. When the bucket intrudes into the warning area, a warning is sounded, and a hydraulic cylinder is controlled so that the work machine stops.